Proposed habitat specific distribution model for red foxes in Tasmania.

From: Sarre SD, MacDonald AJ, Barclay C, Saunders GR, Ramsey DSL. Foxes are now widespread in Tasmania: DNA detection defines the distribution of this rare but invasive carnivore. J Appl Ecol. 2012;50:459-68.

Background

The European red fox (Vulpes vulpes) became established on mainland Australia after a series of introductions after 1845. It now exists as a widespread mainland population that contributes to the declining conservation status of some small to medium sized vertebrates.

On the 31st May 1998 the incursion of a single fox occurred in Tasmania. The fox, believed to have originated at Webb Dock in Melbourne, escaped a cargo vessel at the port of Burnie. The incident was corroborated by video footage and physical evidence of fox prints. However, given the incursion occurred outside the fox breeding season, a single fox at large did not constitute a realistic threat of a population establishing in Tasmania.

In 2001 the Tasmanian Parks and Wildlife Service announced that between 11-19 foxes had been deliberately released into the Tasmanian environment by known persons. Although the Tasmanian Police found no evidence to support this claim, a media campaign and dedicated phone hotline was established in order to encourage members of the public to report fox sightings and physical evidence of foxes. In the same year a number of examples of  opportunistically acquired and post mortem evidence were dismissed as hoaxes that used foxes sourced from the Australian mainland. However, some exhibits were believed by the Tasmanian government to be credible ‘hard evidence’ of an extant fox population, although none could be linked conclusively to the Tasmanian landscape.

A fox eradication program began in Tasmania during 2003 using poison baits in response to a growing belief that numerous foxes were present at multiple locations. This perception was based in part upon a large number of anecdotal sightings reported by members of the public in response to a growing media campaign.

In the absence of data confirming the direct observation of living (‘extant’) foxes in the Tasmanian environment, by 2005 scat mtDNA became the most critical empirical evidence backing the hypothesis that foxes were present. Scat detection dogs were trained to locate specimens using large numbers of fox scats imported from mainland Australia. Attempts to identify species-specific mitochondrial DNA within fox scats located in Tasmania saw approximately 10,000 scats collected in total. In 2012, using 9 unspecified cases of opportunistically acquired post mortem evidence and 56 scats assumed to be fox positive (revising the 61 claimed to be fox positive in mid 2012), Sarre et al. at the University of Canberra’s Invasive Animal’s CRC produced a habitat-specific model of Tasmanian fox distribution and concluded that foxes were now widespread. The distribution of foxes was assumed to be associated with common flora and geomorphology that the authors believed should be targeted with more widespread and intense 1080 baiting.

A reality check on eradication success

The eradication of established invasive species on large land masses has rarely been achieved. Of some 1,129 attempts to eradicate plant and animal species worldwide approximately 97% were attempted on small islands with few successful examples existing for those approaching 1% (685 km2) of the Tasmanian landmass. The coypu (Myocastor coypus) in Britain is a rare example where a vertebrate pest of restricted occupancy has been eradicated from an area larger than this. Importantly, this was achieved given a capacity to survey the response of a target population to the eradication technique that had a known in situ efficacy. In contrast, the capacity to eradicate foxes is not encouraging. While foxes have been eradicated from islands up to 32 km2 in area in Western Australia (0.047% of the Tasmanian landmass) this was achieved by using aerial baiting with fresh meat baits containing 1080. When buried baiting, as used in Tasmania, was used on Phillip Island, Victoria  (0.15% of the Tasmanian landmass) its has yet to cause the eradication of foxes. In contrast with prior experience and reports of success relative to scale, the Tasmanian FEP’s claim is extraordinary. Without empirical data indicating either the effectiveness of their chosen eradication technique, or a proven means of detecting or monitoring the response of the putative population to lethal control, they currently claim to be capable of eradicating foxes on an unprecedented scale.

The eradication of the coypus in the UK (yellow) stands as a rare example of a program that succeeded the eradication of an established pest in a large landmass.

Sandro Bertolino (2006) Daisie Factsheet

Translocation of a single fox from Webb Dock in Melbourne to the Port of Burnie in 1998.

In 2001 the Tasmanian Parks and Wildlife Service claims that a malicious release of between 11-19 foxes had occurred.